The present invention relates to a turnbuckle and, more particularly, to a turnbuckle that can be easily manufactured at low costs and that has excellent pull-resistant and torque-resistant properties. The present invention also relates to a method for making such a turnbuckle.
FIG. 1 shows a conventional turnbuckle 1 that is generally utilized in machine industry, building industry, shipping, etc. to tighten an object such as a machine frame, a molding plate, or a rope. The turnbuckle 1 includes two coupling ends 5 and a pair of spaced interconnecting rods 2 between the coupling ends 5. A longitudinal through-hole 7 is defined between the interconnecting rods 2. Each coupling end 5 has a screw hole 6 through which a screw rod 8 extends. Formed on an outer end of each screw rod 8 is a hook 4. For tightening, a tool 3 (FIG. 2) in the form of a rod is inserted through the through-hole 7 and then turned in a direction to rotate the turnbuckle 1 and, thus, move the hooks 4 toward each other to provide the required tightening effect. However, the interconnecting rods 2 are liable to deform (FIG. 3), causing damage to the turnbuckle 1 and, thus, shortening of the life of the turnbuckle 1.
Such a turnbuckle 1 is generally formed of zinc-aluminum alloy by pressure casting that is time-consuming and expensive. In addition to weak structure with a poor extensibility, the turnbuckle 1 formed by pressure casting is solid and heavy and, thus, less desirable to users. A turnbuckle made by forging has excellent structural strength, but the costs are high.
U.S. Pat. No. 5,908,261 to Bush et al. discloses a turnbuckle and a method of making a turnbuckle. To increase the structural strength of the turnbuckle, elongate fibers are wound around fiber supports on opposite sides of the end fittings that are set in a suitable mold or die cavity. Uncured or liquid matrix material such as thermoplastic or thermoset resin is introduced over the end fittings in the cavity by injection molding or resin transfer molding processes. The matrix material is then allowed to cure or harden to solid form. Such a method is complicated, time-consuming and expensive, and, thus, not suitable for mass production.
A need exists for a method for manufacturing a turnbuckle with enhanced structural strength at low costs without sacrificing the extensibility.